The present invention relates to a room temperature-curable organopolysiloxane composition or, more particularly, to an organopolysiloxane composition excellently stable in storage but curable at room temperature by the mechanism of dealcoholation condensation in the presence of the atmospheric moisture and capable of exhibiting strong adhesion to the substrate surface on which it has been cured.
Several classes of room temperature-curable organopolysiloxane compositions, referred to as the RTV compositions hereinbelow, are known in the prior art as classified according to the mechanism of the reaction for the crosslink formation. In particular, one of the most important classes include the so-called dealcoholation type RTV compositions comprising a diorganopolysiloxane, of which each of the silicon atoms at the molecular chain terminals has a hydroxy group directly bonded thereto, as the base ingredient, a trialkoxysilane compound such as methyl trimethoxy silane as a crosslinking agent, and a catalytically active compound which may be an organic titanium compound or an organic chelate compound of titanium. The crosslinking reaction in the RTV composition of this type proceeds by the dealcoholation condensation in the presence of atmospheric moisture between the silanolic hydroxy groups in the diorganopolysiloxane and the alkoxy groups in the crosslinking agent producing an alcohol as the condensation by-product to give a cured composition having rubbery elasticity. By virtue of the absence of corrosiveness and offensive odor as the nature of the alcohol as the condensation by-product, the RTV compositions of this type are widely used as an adhesive or other materials in the electric and electronic industries.
The RTV compositions of the dealcoholation type, of course, are not free from several disadvantages and problems. For example, the curing velocity thereof is usually not high enough and, in particular, complete curing of the composition can hardly be obtained in the core portion of a thick body. Moreover, the storage stability of the composition is relatively low so that the composition gradually loses curability after a long period of storage even under an anhydrous condition.
Various attempts and proposals have been made hitherto to improve the dealcoholation type RTV compositions in the above mentioned regards. For example, admixture of a special dialkoxy silane compound is proposed to work as a so-called silane scavenger in the dealcoholation type RTV composition improving the curability and storage stability of the composition. If not to mention the expensiveness of such a special silane compound, no sufficient improvement of the storage stability can be obtained by the addition thereof unless the silane compound has one or more of hydrolyzable groups having higher reactivity than the alkoxy groups, such as amido and amino groups. Introduction of such groups to the silane compound is of course detrimental in respect of the corrosiveness and offensive odor of the composition so that the usefulness of the composition may be greatly decreased as a material used in the electric and electronic industries.